Auxiliary devices having cords, such as earphones, mice, keyboards, etc., are used in many electronic devices. In order to use more conveniently, cord winding modules have been increasingly provided in these auxiliary devices for receiving cords or signal wires. The cord winding module typically comprises a rotary wheel, a coil spring and a stopper mechanism. The cord is wound on the rotary wheel, and can be automatically retracted under the elastic restoring force of the coil spring. In the retracting process, the stopper mechanism can prevent the rotary wheel from rotating and stop the retracting of the cord, so that a suitable length of the cord can be reserved without retraction.
There are many types of stopper mechanisms in the prior art, one of which is a ball-rail type. A rail wheel is provided in cooperation with the rotary wheel, and a rail for the moving of a ball is provided on the end surface (the surface perpendicular to the rotating shaft) of the rail wheel. This design will inevitably increase the thickness of the cord winding module in the direction of the rotating shaft and is not suitable for products having a small thickness.